As shown in FIG. 1, a television (TV) receiver 10 is provided with an input terminal 12 for receiving a radio frequency (RF) signal from an antenna or a cable system. The RF signal is applied to a plurality of receiving circuits 14 including a tuner, intermediate frequency (IF) circuits and a video detector stage. A composite video baseband signal CVBS from the video detector stage is applied to a luma/chroma separator 18. The luma/chroma separator 18 separates the composite video signal CVBS into a luma component Y and a chroma component C. In the NTSC format, the bandwidth of the luma component recovered from a composite video baseband signal is about 4.2 MHz (or 330 lines of horizontal resolution).
A luma/chroma processor 24 translates the luma and chroma component signals Y and C into a set of red, green and blue picture tube drive signals R, G. and B. The R, G and B signals are amplified by an output stage 26 and applied to a picture tube 28.
A block 30, coupled to receive the composite video signal CVBS, includes the sync separator and deflection circuits. The circuits 30 develop a pair of horizontal and vertical deflection signals HDS and VDS. The horizontal and vertical deflection signals HDS and VDS are applied to a pair of deflection windings 32 disposed about the neck portion of the picture tube 28.
The kinescope 28, coupled to receive the red, green and blue drive signals R, G and B and responsive to the horizontal and vertical deflection signals HDS and VDS, produces color images on a screen 34.
Recently, higher definition TV systems (e.g., S-VHS and ED-BETA) have been introduced that provide already-separated luma and chroma, or Y/C signals. A feature of these new systems is that the luma signal has a considerably wider bandwidth (as compared to a 4.2 MHz bandwidth of a luma signal derived from an NTSC composite video baseband signal). Illustratively, the luma signal provided by the S-VHS system has a bandwidth of about 5.1 MHz (i.e., 400 lines of horizontal resolution). The luma signal provided by the ED-BETA system, on the other hand, has a bandwidth of about 6.4 MHz (i.e., 500 lines of resolution).
Typically, a standard color TV receiver is not equipped to handle these externally-supplied wideband luma and chroma signals. It is possible to combine these externally-supplied wideband Y/C signals into a composite video baseband signal in the NTSC format, and apply it to the luma/chroma separator 18. Because the luma/chroma separation process is inevitably imperfect in practice, there is always some possibility of cross contamination. The presence of the luma signal in the chroma channel is known as cross-color. The presence of the chroma signal in the luma channel manifests itself as hanging or crawling dots on the TV screen.
In accordance with this invention, a video selector or Y/C switch is provided which has input terminals for receiving the internally-separated luma and chroma signals Y.sub.1 and C.sub.1, as well as the 6 externally-supplied wideband luma and chroma signals Y.sub.2, C.sub.2 and Y.sub.3, C.sub.3. The video switch selects a pair of input component signals for application to its output terminals in response to a control signal FCS.
Pursuant to a further feature of this invention, means are provided for disabling the luma/chroma separator circuits when the video selector switch selects a pair of externally-supplied component signals for application to its output terminals.